The long-term goal of this program project is to improve understanding of the pathogenesis and pathophysiology of childhood cancers and to capitalize on molecular insights gained in the laboratory to devise new means of assessing prognosis and improving therapy. This broad objective is being pursued through five coordinated projects supported by administrative, transgenic, molecular cytogenetic and molecular diagnostic cores. In Project 1 (M. Roussel) the aim is to clarify the role of INK4 inhibitors of the CDK4/CDK6 cyclin D-dependent kinases in the genesis of childhood cancers. Each known member of the INK4 family arrests the progression of cells through the first gap (G1 phase of the cell cycle, but their contribution to tumorigenesis remains to be defined. Project 2 (S. Baker) will address the role of the EWS-ets family of chimeric transcription factors in the aberrant growth and differentiation of Ewing's sarcoma. EWS interacting proteins will be identified and cell types susceptible to transformation by the fusion protein will be defined in transgenic mice. The working hypothesis of Project 3 (J. Downing) is that AML1 fusion proteins contribute to leukemia by interfering with target genes normally regulated by the AML1/CBFbeta complex. This role will be clarified by defining the normal function of the AML1 gene in embryologic and hematopoietic cell development. The intent of Project 4 (D. Shapiro) is to identify the apparently diverse mechanisms by which the PAX3-FKHR oncoprotein transforms myogenic cells leading to alveolar rhabdomyosarcoma. Novel in vitro models have been developed to assess the effects of enforced PAX3-FKHR expression of myogenic differentiation. Project 5 (A.T. Look) will rely on fluorescence in situ hybridization and other molecular approaches to identify and characterize the properties of a putative neuroblastoma suppressor locus on chromosome 1p. This 5-year program seeks to integrate the efforts of leading molecular biologists with comprehensive core services to answer pivotal questions about the mechanisms that drive childhood neoplasia. Its underlying concept is that malignant transformation involves diverse signaling pathways that must be identified before we will know the legitimate targets for therapeutic or preventive intervention.